TETRAHYDROPYRIDOINDOLE DERIVATIVES

Abstract

The invention relates to tetrahydropyridoindole derivatives and their use as active ingredients in the preparation of pharmaceutical compositions. The invention also concerns related aspects including processes for the preparation of the compounds, pharmaceutical compositions comprising one or more of those compounds and methods of treatment comprising administration of said compounds.

Full Text

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Tetrahydropyridoindole derivatives
Field of the invention:
The present invention relates to novel tetrahydro pyridoindole derivatives and their use as potent CRTH2 receptor antagonists in the treatment of prostaglandin mediated diseases, to pharmaceutical compositions comprising these derivatives and to processes for their preparation. In particular, such derivatives may be used alone or in pharmaceutical compositions for the treatment of both chronic and acute allergic/immune disorders such as allergic asthma, rhinitis, chronic obstructive pulmonary disease (COPD), dermatitis, inflammatory bowel disease, rheumatoid arthritis, allergic nephritis, conjunctivitis, atopic dermatitis, bronchial asthma, food allergy, systemic mast cell disorders, anaphylactic shock, urticaria, eczema, itching, inflammation, ischemia-reperfusion injury, cerebrovascular disorders, pleuritis, ulcerative colitis, eosinophil-related diseases, such as Churg-Strauss syndrome and sinusitis, basophil-related diseases, such as basophilic leukemia and basophilic leukocytosis in humans and other mammals.
Background of the invention:
Prostaglandin D2 is a known agonist of the thromboxane A2 (TxA2) receptor, the PGD2 (DP) receptor and the recently identified G-protein-coupled "chemoattractant receptor-homologous molecule expressed on Th2 cells" (CRTH2).
The response to allergen exposure in a previously sensitized host results in a cascade effect involving numerous cell types and release of a number of cytokines, chemokines, and multiple mediators. Among these critical initiators are the cytokines interleukin (IL)-4, IL-13, and IL-5, which play critical roles in Th2 cell differentiation, immunoglobulin (Ig)E synthesis, mast cell growth and differentiation, upregulation of CD23 expression, and the

differentiation, recruitment, and activation of eosinophils. The stimulated release of the array of mediators, causes end-organ damage, including constriction and hyperresponsi-veness, vascular permeability, edema, mucous secretion, and further inflammation.
Because of the number of responses targeted, corticosteroids have proven to be the most effective therapy. Rather than antagonizing these specific responses in a directed way, another approach is to alter the immune response, that is, to change the nature of the immunological response to allergen. CRTH2 is preferentially expressed on Th2 cells and is a chemoattractant receptor for PGD2 that mediates PGD2-dependent migration of blood Th2 cells. Chemoattractants are responsible for the recruitment of both Th2 cells and other effector cells of allergic inflammation, which can provide the conceptual basis for the development of new therapeutic strategies in allergic conditions.
So far, few compounds having CRTH2 antagonistic activity have been reported in the patent literature. Bayer AG claims the use of Ramatroban ((3R)-3-(4-fluorobenzene-sulfonamido)-l,2,3,4-tetrahydrocarbazole-9-propionic acid) for the prophylaxis and treatment of allergic diseases, such as asthma, allergic rhinitis or allergic conjuvatitis (GB 2388540). Further, (2-tert.-butoxycarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid and (2-ethoxycarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid are disclosed by Kyle F. et al in two patent applications (US 5817756 and WO 9507294, respectively).
Furthermore, oral bioavailability of the Ramatroban and its ability to inhibit prostaglandin D2-induced eosinophil migration in vitro has been reported (Journal of Pharmacology and Experimental Therapeutics, 305(1), p.347-352 (2003)).
Description of the invention:
It has now been found that compounds of the general Formulae (I) and (II) of the present invention are CRTH2 receptor antagonists. These compounds are useful for the treatment of both chronic and acute allergic/immune disorders such as allergic asthma, rhinitis, chronic obstructive pulmonary disease (COPD), dermatitis, inflammatory bowel disease,

The compounds of general Formulae (I) and (II), especially those mentioned as being preferred, are efficacious in vitro, inhibiting PGD2-induced migration of eosinophils or other CRTH2 expressing cells in a cell migration assay. A number of techniques have been developed to assay such chemotactic migration (see, e.g., Leonard et al., 1995, "Measurement of a- and p-Chemokines", in Current Protocols in Immunology, 6.12.1-6.12.28, Ed. Coligan et al., John Wiley & Sons, Inc. 1995). The compounds of the present invention are tested using a protocol according to H. Sugimoto et al. (J Pharmacol Exp Ther. 2003,305(1), 347-52), or as described hereinafter: Purified eosinophils are labeled with a fluorescent dye, i.e. Calcein-AM and loaded in BD Falcon FluoroBlock upper inserts. Test compounds are diluted and incubated with eosinophils in the BD Falcon FluoroBlock upper inserts for 30 min at 37 °C in a humidified CO2 incubator. A constant amount of PGD2 is added to BD Falcon FluoroBlock lower chamber, at a concentration known to have a chemotactic effect on CRTH2 cells. As a control, at least one aliquot in the upper well does not contain test compound. The inserts are combined with the chambers and are incubated for 30 min at 37 °C in a humidified CO2 incubator. After an incubation period, the number of migrating cells on the lower chamber is counted using a fluorescent reader, i.e. an Applied Biosystems Cyto Fluor 4000 plate reader. The contribution of a test compound to the chemotactic activity of PGD2 is measured by comparing the chemotactic activity of the aliquots containing only dilution buffer with the activity of aliquots containing a test compound. If addition of the test compound to the solution results in a decrease in the number of cells detected in the lower chamber relative to the number of cells detected using a solution containing only PGD2, then there is identified an antagonist of PGD2 induction of chemotactic activity of eosinophils.
The compounds of general Formulae (I) and (II), especially those mentioned as being preferred, are efficacious in vivo by suppressing allergic reactions in ovalbumin sensitized animals, such as eosinophil infiltration into the lung, coughing, and improving respiratory function. Such animal models are known to a skilled person, see e.g. W. Elwood et al. (Int. Arch. Allergic Immunol. 1992, 99, 91-97).

The following paragraphs provide definitions of the various chemical moieties that make up the compounds according to the invention and are intended to apply uniformly throughout the specification and claims unless an otherwise expressly set out definition provides a broader definition.
The term "C1-C5-alkyl", alone or in combination with other groups, means a straight-chain or branched-chain alkyl group with 1-5 carbon atoms as for example methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert.-butyl, isobutyl and the isomeric pentyls. Preferred are groups with 1 to 3 carbon atoms. This C1-C5-alkyl group may optionally be substituted by one to three substituents independently selected from cyano, halogen, hydroxy, cycloalkyl, aryl, C2-C5-alkenyl, C1-C5-alkoxy, C2-C5-alkenyloxy, trifluoromethyl, trifluoromethoxy, amino and carboxy. If C1-C5-alkyl is substituted, it preferably represents trifluoromethyl.
The term "C0-C5-alkyl-carbonyl", alone or in combination with other groups, means an R-CO- group, wherein R is hydrogen or a C1-C5-alkyl group as defined above; examples are formyl, acetyl, propionyl, butyryl, isobutyryl and the like.
The term "C2-C5-alkenyl-carbonyl", alone or in combination with other groups, means an R'-CO- group, wherein R' is a straight-chain or branched-chain alkenyl group with 2 to 5 carbon atoms; examples are acryl, methacryl, crotonoyl and dimethylacryl.
The term "C1-C5-alkyl-carbamoyr, alone or in combination with other groups, means an R"-NH-CO- group wherein R" is a C1-C5-alkyl group as defined above; examples are methylcarbamoyl, ethylcarbamoyl, propylcarbamoyl, isopropylcarbamoyl, butylcarbamoyl, tert.-butylcarbamoyl and the like.
The term "C1-C5-alkoxy", alone or in combination with other groups, means a group of the Formula R"-O- in which R" is a C1-C5-alkyl group as defined above; examples are

methoxy, ethoxy, n-propoxy, isopropoxy, --butoxy, isobutoxy, sec-butoxy and tert-butoxy, preferably methoxy and ethoxy.
The term "aryl", alone or in combination with other groups, means an aromatic carbocyclic group from 6 to 14 carbon atoms having a single ring or multiple condensed rings wherein said ring(s) is/are optionally substituted by one or more substituents independently selected from the group consisting of oxo, cyano, halogen, hydroxy, C1-C5-alkyl, C2-C5-alkenyl, Ci-C5-alkoxy, C2-C5-alkenyloxy, cycloalkyl, aryl, heteroaryl, trifluoromethyl, trifluoromethoxy, amino and carboxy. Preferred aryl include phenyl or naphthyl which optionally carry one or more substituents, preferably one or two substituents, each independently selected from cyano, halogen, hydroxy, C1-C5-alkyl, C2-C5-alkenyl, C1-C5-alkoxy, C2-C5-alkenyloxy, cycloalkyl, aryl, heteroaryl, trifluoromethyl, trifluoromethoxy, amino and carboxy.
The term "aryl-C1-C5-alkyl", alone or in combination with other groups, means a C1-C5-alkyl group having an aryl substituent in which the aryl group is as defined above.
The term "aryl-carbonyl", alone or in combination with other groups, means a group of the Formula Ar-CO- in which Ar is an aryl group as defined above; examples are phenyl-carbonyl and naphthyl-carbonyl.
The term "aryl-C1-C5-alkyl-carbonyl', alone or in combination with other groups, means a C1-C5-alkyl-carbonyl group having an aryl substituent in which the aryl group is as defined above.
The term "aryl-C1-C5-alkoxy-carbonyl", alone or in combination with other groups, means a C1-C5-alkoxy-carbonyl group having an aryl substituent in which the aryl group is as defined above.

The term "aryl-carbamoyl", alone or in combination with other groups, means a group of the Formula Ar-NH-CO- in which Ar is an aryl group as defined above.
The term "aryl-thiocarbamoyl", alone or in combination with other groups, means a group of the Formula Ar-NH-C(=S)- in which Ar is an aryl group as defined above.
The term "aryl-C1-C5-alkyl-carbamoyl", alone or in combination with other groups, means a group of the Formula Ar-C1-C5-alkyl-NH-CO- in which Ar is an aryl group as defined above.
The term "aryl-C1-C5-alkyl-thiocarbamoyl", alone or in combination with other groups, means a group of the Formula Ar-C1-C5-alkyl-NH-C(=S)- in which Ar is an aryl group as defined above.
The term "cycloalkyl", alone or in combination with other groups, means a saturated cyclic hydrocarbon moiety containing 3-15, preferably 3-6, carbon atoms, optionally substituted by one or more groups, each individually and independently selected from C2-C5-alkenyl, C1-C5-alkoxy, C1-C5-alkoxy-C1-C5-alkyl, C1-C5-alkoxy-carbonyl, C1-C5-alkoxy-carbonyl-C1-C5-alkyl, C1-C5-alkyl, C0-C5-alkyl-carbonyl, C0-C5-alkyl-carbonyl-C1-C5-alkyl, C0-C5-alkyl-carbonyloxy, C1-C5-alkylendioxy, C1-C5-alkylsulfinyl, C1-C5-alkylsulfinyl-C1-C5-alkyl, C1-C5-alkyIsulfonyl, C1-C5-alkylsulfonyl-C1-C5-alkyl, C1-C5-alkylthio, C1-C5-alkylthio-C1-C5-aIkyl, C2-C5-alkynyl, amino, amino-C1-C5-alkyl, aminocarbonyl, aminocarbonyl-C1-C5-alkyl, aryl, aryl-C2-C5-alkenyl, aryl-C1-C5-alkoxy, aryl-C1-C5-alkyl, aryloxy, aryloxycarbonyl, aryloxycarbonyl-C1-C5-alkyl, arylsulfinyl, arylsulfinyl-C1-C5-alkyl, arylsulfonyl, arylsulfonyl-C1-C5-alkyl, arylthio, arylthio-C1-C5-alkyl, carboxy, carboxy-C1-C5-alkyl, cyano, cyano-C1-C5-alkyl, formyl, formyl-C1-C5-alkyl, halogen, haloalkoxy, halo-C1-C5-alkyl, hydroxy, hydroxyl-C1-C5-alkyl, mercapto, and nitro. Preferably, cycloalkyl is unsubstituted. Representative examples of cycloalkyl include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and

cyclooctyl, preferably cyclopropyl, cyclopentyl and cyclohexyl. In polycyclic cycloalkyl groups one of the distal rings may be aromatic, e.g., 1-indanyl, 2-indanyl, tetrahydronaphthalene, and the like.
The term "cycloalkyl-carbonyl", alone or in combination with other groups, means a carbonyl group having a cycloalkyl substituent in which the cycloalkyl group is as defined above.
The term "cycloalkyl-C1-C5-alkyl-carbonyl", alone or in combination with other groups, means a C1-C5-alkyl-carbonyl group having a cycloalkyl substituent in which the cycloalkyl group is as defined above.
The term "cycloalkyl-C1-C5-alkoxy-carbonyl", alone or in combination with other groups, means a C1-C5-alkoxy-carbonyl group having a cycloalkyl substituent in which the cycloalkyl group is as defined above.
The term "cycloalkyl-carbamoyl", alone or in combination with other groups, means a group of the Formula cycloalkyl-NH-C(=S)- wherein the cycloalkyl group is as defined above.
The term "heteroaryl" means a monocyclic heteroaromatic, or a bicyclic or (less preferred) a tricyclic fused-ring heteroaromatic group having preferably 5 to 14, especially 5 to 10 ring members of which 1 to 3, especially 1 or 2, are heteroatoms selected from the group consisting of oxygen, nitrogen and sulphur, while the remaining ring members are carbon atoms. Heteroaryl is optionally substituted by one or more substituents, preferably one or two substituents, each independently selected from cyano, halogen, hydroxy, C1-C5-alkyl, C2-C5-alkenyl, C1-C5-alkoxy, C2-C5-alkenyloxy, cycloalkyl, aryl, heteroaryl, trifluoromethyl, trifluoromethoxy, amino and carboxy. Particular examples of heteroaromatic groups include pyridyl, pyrazinyl, pyrrolyl, fiiryl, thienyl, imidazolyl,

oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadia-zolyl, 1,2,5-oxadiazolyl, l,3,4-oxadiazolyl,l,3,4-triazinyl, 1,2,3-triazinyl, benzofuryl, [2,3-dihydro]benzofuryl, isobenzofuryl, benzothienyl, benzotriazolyl, isobenzothienyl, indolyl, isoindolyl, 3H-indolyl, benzimidazolyl, imidazo[l,2-a]pyridyl? benzothiazolyl, benzoxa-zolyl, quinolizinyl, quinazolinyl, phthalazinyl, quinoxalinyl, cinnolinyl, naphthyridinyl, pyrido[3,4-b]pyridyl, pyrido[3,2-b]pyridyl, pyrido[4,3-b]pyridyl, quinolyl, isoquinolyl, tetrazolyl, purinyl, pteridinyl, carbazolyl, xanthenyl or benzoquinolyl. Preferred heteroaryl groups include thienyl, pyridyl or furyl, wherein said groups optionally carry one or more substituents, preferably one or two substituents, each independently selected from cyano, halogen, hydroxy, C1-C5-alkyl, C2-C5-alkenyl5 C1-C5-alkoxy, C2-Cs-alkenyloxy, cycloalkyl, aryl, heteroaryl, trifluoromethyl, trifluoromethoxy, amino and carboxy.
The term "heteroaryl-C1-C5-alkyl", alone or in combination with other groups, means a Ci-Cs-alkyl group having a heteroaryl substituent in which the heteroaryl group is as defined above.
The term "heteroaryl-carbonyl", alone or in combination with other groups, means a group of the Formula Het-CO- in which Het is a heteroaryl group as defined above.
The term "heteroaryl-C1-C5-alkyl-carbonyl", alone or in combination with other groups, means a group of the Formula Het-C1-C5-alkyl-CO- in which Het is a heteroaryl group as defined above.
The term "heteroaryl-C1-C5-alkoxy-carbonyr, alone or in combination with other groups, means a group of the Formula Het-C1-C5-alkoxy-CO- in which Het is a heteroaryl group as defined above.

The term "halogen" means fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine and bromine.
Salt-forming groups are groups or radicals having basic or acidic properties. Compounds having at least one basic group or at least one basic radical, for example amino, a secondary amino group not forming a peptide bond or a pyridyl radical, may form acid addition salts, for example with inorganic acids. When several basic groups are present mono- or poly-acid addition salts may be formed.
Compounds having acidic groups, such as a carboxy group or a phenolic hydroxy group, may form metal or ammonium salts, such as alkali metal or alkaline earth metal salts, for example sodium, potassium, magnesium or calcium salts, or ammonium salts with ammonia or suitable organic amines, such as tertiary monoamines, for example triethylamine or tri-(2-hydroxyethyl)-amine, or heterocyclic bases, for example N-ethyl-piperidine or N,N'-dimethylpiperazine. Mixtures of salts are possible.
Compounds having both acidic and basic groups can form internal salts.
For the purposes of isolation or purification, as well as in the case of compounds that are used further as intermediates, it is also possible to use pharmaceutically unacceptable salts, e.g. the picrates. Only pharmaceutically acceptable, non-toxic salts may be used for therapeutic purposes, however, and those salts are therefore preferred.
The expression "pharmaceutically acceptable salts" encompasses either salts with inorganic acids or organic acids like hydrochloric or hydrobromic acid, sulfuric acid, phosphoric acid, citric acid, formic acid, acetic acid, maleic acid, tartaric acid, benzoic acid, methanesulfonic acid, p-toluenesulfonic acid, and the like that are non-toxic to living organisms. In case the compound of general Formula (I) is acidic in nature the expression encompasses salts with

an inorganic base like an alkali or earth alkali base, e.g. sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like which are also non-toxic to living organisms.
A first aspect of the present invention relates to novel tetrahydropyridoindole derivatives of the general Formula (I):

Any reference hereinabove or hereinbelow to a compound of general Formula (I) or (II) is to be understood as referring also to optically pure enantiomers, mixtures of enantiomers, racemates, optically pure diastereoisomers, mixtures of diastereoisomers, diastereoisomeric racemates, mixtures of diastereoisomeric racemates, meso forms and salts [only pharmaceutically acceptable ones in case of a compound of general Formula (II)] of such compounds, as appropriate and expedient.
Preferred tetrahydropyridoindole derivatives of general Formula (I) are those wherein R1, R2 , R3 and R4 represent hydrogen.
In a preferred embodiment, R , R , R and R independently represent C1-C5-alkyl, C1-C3-alkoxy, halogen, nitro, cyano or formyl, especially C1-C5-alkyl, C1-C3-alkoxy or halogen.
In another preferred embodiment one or two substituents selected from R1 , R2 , R3 and R4 independently represent methyl, trifluoromethyl, methoxy, fluoro, chloro or bromo.
In a very preferred embodiment R is selected from C1-C5-alkyl, C1-C5-alkoxy, halogen and trifluoromethyl, especially from C1-C5-alkyl, halogen and trifluoromethyl; R is hydrogen or halogen, especially hydrogen; and R1 and R4 are both hydrogen.
In a most especially preferred embodiment R is selected from methyl, fluoro, chloro, bromo and trifluoromethyl; R3 is hydrogen or chloro, especially hydrogen; and R and R are both hydrogen.
In a particularly preferred embodiment, R5 is selected from the group consisting of 2-cyclohexyl-2-phenyl-acetyl; 2-naphthalen-l-yl-acetyl; 2-naphthalen-2-yl-acetyl; 3-cyclopentyl-propionyl; 3-phenyl-propionyl; acetyl; diphenylacetyl; hexanoyl; (E)-but-2-enoyl; 9i/-fluoren-9-ylmethoxycarbonyl; benzyloxycarbonyl; butoxycarbonyl; 3-phenyl-propyl; phenethyl; phenylacetyl; ethylcarbamoyl; 2-bromo-3-methyl-benzoyl; 2-bromo-5-methyl-benzoyl; 2-methoxy-benzoyl; 3,4,5-trimethoxy-benzoyl; 3,5-bis-trifluoromethyl-benzoyl; 3,5-dimethoxy-benzoyl; 3-chloro-benzoyl; 4-bromo-benzoyl; 4-chloro-benzoyl; 4-methoxy-benzoyl; 4-tert.-butyl-benzoyl; 4-trifluoromethoxy-benzoyl; 4-trifluoromethyl-

benzoyl; benzoyl; phenylcarbamoyl; 4'-ethyl-biphenyl-4-carbonyl; biphenyl-2-carbonyl; biphenyl-4-carbonyl; 2-methoxy-naphthaIene-1 -carbonyl; 4-methoxy-naphthalene-1 -carbonyl; 2-ethoxy-naphthalene-l-carbonyl; naphthalene-1-carbonyl; cyclohexane-carbonyl; cyclopropane-carbonyl; pyridine-3-carbonyl; 2-chloro-6-methyl-pyridine-4-carbonyl; pyridine-4-carbonyl; furan-2-carbonyl; furan-3-carbonyl; 2-methyl-furan-3-carbonyl; 3-methyl-furan-2-carbonyI; 5-bromo-furan-2-carbonyl; pyrazine-2-carbonyl, benzo[b]thiophene-2-carbonyl; 5-chloro-thiophene-2-carbonyl; 3-methyl-thiophene-2-carbonyl; 5-methyl-thiophene-2-carbonyl; thiophene-2-carbonyl and thiophene-3-carbonyl.
Very preferably R5 represents phenyl-carbonyl or naphthyl-carbonyl (especially naphthalene-1-carbonyl), wherein the phenyl or naphthyl moiety is optionally substituted by one or more, especially by one or two, substituents selected from C1-C5-alkyl, C1-C5-alkoxy and halogen. If R5 represents substituted phenyl-carbonyl, the substituents are preferably selected from C1-C5-alkyl, such as especially methyl, and halogen, such as especially fluoro, chloro and bromo. If R5 represents substituted naphthyl-carbonyl, the substituents are preferably selected from C1-C5-alkoxy, such as especially methoxy and ethoxy, and halogen, such as especially fluoro,
A group of preferred compounds are those wherein R , R , R and R represent hydrogen, R5 represents a C1-C5-alkoxy-carbonyl group, an aryl-C1-C5-alkyl-carbonyl group, an aiyl-carbonyl group or a heteroaryl-carbonyl group, especially an aryl-carbonyl group, very preferably naphthalene- 1-carbonyl.
Another group of preferred compounds are those wherein R , R , R and R represent hydrogen and R5 represents a C1-C5-alkoxy-carbonyl group, a phenyl C1-C5-alkyl-carbonyl group, a naphthalene-1-carbonyl group or a thiophene-2-carbonyl group.
In a preferred embodiment the present invention relates to tetrahydropyridoindole
derivatives of the general Formula (I), wherein
R1, R2, R3 and R4 independently represent hydrogen, C1-C5-alkyl, C1-C3-alkoxy or halogen;
and

R5 represents C0-C5-alkyl-carbonyl; C1-C5-alkyl-carbamoyl; C1-C5-alkoxy-carbonyl; C2-C5-alkenyl-carbonyl; C3-C6-cycloalkyl-carbonyl; C3-C6-cycloalkyl-C1-C3-alkyl-carbonyl; C3-C6-cycloalkyl-carbamoyl; C3-C6-cycloalkyl-thiocarbamoyl; phenyl-C1-C3-alkyl; phenyl-carbonyl or phenyl-C1-C3-alkyl-carbonyl wherein the phenyl moiety of these two groups may be mono-, di-, tri- or tetra-substituted by substituents independently selected from Ci-C4-alkyl5 C1-C3-alkoxy, halogen, trifluoromethyl and trifluoromethoxy, mono-substituted by C3-C6-cycloalkyl, or mono-substituted by a phenyl group which in turn may be substituted by a C1-C3-alkyl or C1-C3-alkoxy group; phenyl-C1-C3-alkoxy-carbonyl; phenyl-carbamoyl or phenyl-thiocarbamoyl wherein these two groups are optionally independently mono- or poly-substituted by C1-C5-alkyl and/or halogen; phenyl-C1-C3-alkyl-carbamoyl; phenyl-C1-C3-alkyl-thiocarbamoyl; biphenyl-carbamoyl; naphthyl-carbonyl, naphthyl-C1-C3-alkyl-carbonyl or naphthyl-carbamoyl wherein the naphthyl moieties of these three groups are optionally mono- or poly-substituted by substituents independently selected from C1-C3-alkyl, C1-C3-alkoxy and halogen; fluorenyl-carbonyl, optionally substituted by oxo; fluorenyl-C1-C3-alkoxy-carbonyl; or five- to nine-membered heteroaryl-carbonyl groups containing one to three, preferably 1 or 2, heteroatoms independently selected from oxygen, nitrogen and sulfur wherein said groups may be substituted by one or two groups independently selected from C1-C3-alkyl, C1-C3-alkoxy, halogen and trifluoromethyl;
with the proviso that when R1, R2, R3 and R4 represent hydrogen, R5 is not an ethoxy-carbonyl group or a tert.-butoxycarbonyl group.
The present invention also relates to tetrahydropyridoindole derivatives of the general
Formula (I), wherein
R1, R2, R3 and R4 independently represent hydrogen, C1-C5-alkyl, C1-C3-alkoxy or halogen;
and
R5 represents C0-C5-alkyl-carbonyl; C1-C5-alkoxy-carbonyl; C2-C5-alkenyl-carbonyl; C3-
C6-cycloalkyl-carbonyl; C3-C6-cycloalkyl-C 1-C3-alkyl-carbonyl; C3-C6-Cycloalkyl-C1 -C3-
alkoxy-carbonyl; phenyl-carbonyl or phenyl-C1-C3-alkyl-carbonyl wherein the phenyl
moiety of said groups may be independently mono-, di- or tri-substituted by C1-C4-alkyl,

C1-C3-alkoxy, halogen, trifluoromethyl or trifluoromethoxy, or mono-substituted by a phenyl group which in turn may be substituted by a C1-C3-alkyl or C1-C3-alkoxy group; naphthyl-carbonyl; fluorenyl-C1-C3-alkoxy-carbonyl; or five- or six-membered heteroaryl-carbonyl groups containing one to three heteroatoms independently selected from oxygen, nitrogen and sulfur wherein said groups may be substituted by one or two groups independently selected from C1-C3-alkyl, C1-C3-alkoxy, halogen and trifluoromethyl; with the proviso that when R1 , R2 , R3 and R4 represent hydrogen, R5 is not an ethoxy-carbonyl group or a tert-butoxycarbonyl group.
Examples of preferred compounds of general Formula (I) are selected from the group
consisting of:
(2-benzyloxycarbonyl-l, 2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
(2-butoxycarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
(2-9/f-fluoren-9-ylmethoxycarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic
acid;
(2-acety-1-1, 2, 3, 4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
(2-phenylacetyl-l, 2, 3, 4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
(2-benzoyl-l, 2,3, 4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
[2-(3,4,5-trimethoxy-benzoyl)-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic acid;
(2-cyclohexanecarbonyl-l, 2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
[2-(4-methoxy-benzoyl)-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic acid;
[2-(thiophene-2-carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(furan-2-carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
(2-cyclopropanecarbonyl-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
[2-(naphthalene-l-carbonyl)-l,2,3,44etrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(2-methoxy-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(4-trifluoromethyl-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(3,5-bis-trifluoromethyI-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic
acid;
[2-(3-cyclopentyl-propionyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;

R6, R7, R8 and R9 independently represent hydrogen, C1-C5-alkyl, C1-C5-alkoxy, halogen, nitro, cyano or formyl; and
R10 represents Co-C5-alkyl-carbonyl, C2-C5-alkenyl-carbonyl, C1-C5-alkoxy-carbonyl, C1-C5-aikyl, C1-C5-alkyl-carbamoyl, aryl-C1-C5-alkyl, aryl-carbonyl, aryl-C1-C5-alkyl-carbonyl, aryl-C1-C5-alkoxy-carbonyl, aryl-carbamoyl, cycloalkyl-carbonyl, cycloalkyl-Ci-Cs-alkyl-carbonyl, cycloalkyl-C1-C5-alkoxy-carbonyl, heteroaryl-C1-C5-alkyl, heteroaryl-carbonyl, heteroaryl-C1-C5-alkyl-carbonyl or heteroaryl-CrCs-alkoxy-carbonyl.
The present invention also relates to pharmaceutical compositions comprising at least one tetrahydropyridoindole derivative of the general Formula (II), or pharmaceutically acceptable salts thereof, and inert carrier materials and/or adjuvants.
The preferred embodiments described for the compounds of general Formula (I) are also preferred with regard to the pharmaceutical use of the compounds of the present invention such as their use as a medicament and their use in pharmaceutical compositions, especially for the treatment of the diseases mentioned herein.
Pharmaceutical compositions comprising at least one tetrahydropyridoindole derivative of the general Formula (II) are particularly useful for the prevention or treatment of diseases selected from the group consisting of both chronic and acute allergic/immune disorders such as allergic asthma, rhinitis, chronic obstructive pulmonary disease (COPD), dermatitis, inflammatory bowel disease, rheumatoid arthritis, allergic nephritis, conjunctivitis, atopic dermatitis, bronchial asthma, food allergy, systemic mast cell disorders, anaphylactic shock, urticaria, eczema, itching, inflammation, ischemia-reperfusion injury, cerebrovascular disorders, pleuritis, ulcerative colitis, eosinophil-related diseases, such as Churg-Strauss syndrome and sinusitis, and basophil-related diseases, such as basophilic leukemia and basophilic leukocytosis
Another object of the present invention is a method for the treatment or prophylaxis of disease states mediated by CRTH2 comprising the administration to the patient of a

pharmaceutically active amount of a tetrahydropyridoindole derivative according to general Formula (II).
In a preferred embodiment of the invention, said amount is comprised between 1 mg and 1000 mg per day, particularly from 2 mg to 500 mg per day, more particularly from 5 mg to 200 mg per day.
Furthermore, the present invention also concerns a process for the preparation of a pharmaceutical composition comprising at least one tetrahydropyridoindole derivative according to general Formula (II) by mixing one or more active ingredients according to general Formula (II) with inert carrier materials and/or adjuvants in a manner known per se.
The present invention also relates to the use of a tetrahydropyridoindole derivative according to general Formula (II) in the preparation of a medicament for the prevention or treatment of the diseases mentioned herein.
These pharmaceutical compositions can be administered enterally, such as orally (e.g. in the form of tablets, coated tablets, dragees, hard and soft gelatine capsules, solutions, emulsions or suspensions), nasally (e.g. in the form of nasal sprays), rectally (e.g. in the form of suppositories) or dermally. However, the administration can also be effected parenterally, such as intramuscularly or intravenously (e.g. in the form of injection solutions).
Pharmaceutical compositions comprising at least one compound of the general Formula (II) can be processed with pharmaceutically inert, inorganic or organic carrier materials and/or adjuvants for the production of tablets, coated tablets, dragees, and hard gelatine capsules. Lactose, corn starch or derivatives thereof, talc, stearic acid or its salts etc. can be used, for example, as such carrier materials or adjuvants for tablets, dragees, and hard gelatine capsules. Suitable earner materials or adjuvants for soft gelatine capsules, are, for example, vegetable oils, waxes, fats, semi-solid substances and liquid polyols etc..

Suitable carrier materials or adjuvants for the production of solutions and syrups are, for example, water, polyols, saccharose, invert sugar, glucose etc.. Suitable carrier materials or adjuvants for injection solutions are, for example, water, alcohols, polyols, glycerol, vegetable oils, etc.. Suitable carrier materials or adjuvants for suppositories are, for example, natural or hardened oils, waxes, fats, semi-solid or liquid polyols, etc..
The above-described components for orally administered or injectable compositions are merely representative. Further materials as well as processing techniques and the like are set out in Remington's Pharmaceutical Sciences, 20th Edition, 2001, Marck Publishing Company, Easton, Pennsylvania, which is incorporated herein by reference.
These pharmaceutical compositions according to the invention can also be administered in sustained release forms or by using sustained release drug delivery systems.
A further object of the invention is a process for preparing tetrahydropyridoindole derivatives according to general Formula (I). Compounds according to general Formula (I) of the present invention are prepared according to the general sequence of reactions outlined in the schemes below, wherein R , R , R , R and R are as defined in general Formula (I). The compounds obtained may also be converted into a pharmaceutically acceptable salt thereof in a manner known per se.
Compounds of the invention may be manufactured by the application or adaptation of known methods, by which is meant methods used hereinafter or described in the literature, for example those described by Larock R. C. in "Comprehensive organic transformations: a guide to functional group preparations", VCH publishers, (1999).
In the reactions described hereinafter, it may be necessary to protect reactive functional groups, for example hydroxy, amino, imino, thio or carboxy groups, where these are desired in the final product, to avoid their unwanted participation in the reactions. Conventional protecting groups may be used in accordance with standard practice, for

example see Greene T. W. and Wuts P. G. M. in "Protective groups in organic synthesis" Wiley-Interscience (1999).
Generally, tetrahydropyridoindole derivatives of general Formula (I) are prepared as shown in Schemes 1 and 2, by condensing phenylhydrazine of Formula 1 and 4-piperidone monohydrate hydrochloride of Formula 2 in a Fischer indole synthesis to produce tetrahydropyridoindole of Formula 3, using conditions known to a skilled person (e.g. M. H. Block et al., J. Med Chem. (2002), 45, 3509-3523). The nitrogen atom in Formula 3 is protected with a protecting group (PG), such as alkoxycarbonyl, preferably tert-butoxycarbonyl, or benzyloxycarbonyl, under standard conditions, affording a compound of Formula 4. Then, compound of Formula 4 reacts with a compound of Formula L-CH2CO2R in which R is an alkyl group, preferably ethyl or tert.-butyl and L is a leaving group, in the presence of a base, such as caesium carbonate, sodium hydride, potassium tert.-butanolate or the like, in a suitable solvent, such as acetone, tetrahydrofuran or dioxane, to generate a compound of Formula 5. Suitable L is a leaving group such as halo, in particular bromo or chloro; mesyloxy or tosyloxy. Preferably, the compound of Formula L-CH2CO2R is ethyl bromo-acetate. Deprotection under standard conditions delivers an intermediate of Formula 6.

As illustrated in Scheme 2, intermediate of Formula 6 reacts in Step a) with a reagent of Formula L-R5, where R5 is as defined in general Formula (I) hereinabove and L is a leaving group, such as hydroxy, or halo, in particular chloro or bromo. R5 transferring reagent of Formula L-R5 may be a chloroformate (Method A); or an acyl halide, preferably an acid chloride, or bromide, used as such (Method B); or generated in situ from the corresponding acid with a halogenating reagent under conditions known to a skilled person, preferably by means of oxalyl chloride or phosphorous oxychloride (Method C); or an acyl anhydride, transferring R5 in the presence of a base, such as triethylamine, N,N-diisopropylethylamine, N-ethyl-morpholine, N-methylpiperidine, or pyridine, in a suitable solvent, such as dichloro-methane, tetrahydrofurane, or N,N-dimethyiformamide, to give a product of Formula 7.
In another aspect, a carboxylic acid is used in the presence of a coupling reagent (Method D), such as 1,3-dicyclohexylcarbodiimide, diisopropylcarbodiimid, O-(7-azabenzotriazol-1--

yl)-N,N,N',N',-tetramethyluronium hexafluorophosphate and the like, in the presence of a base described hereinabove, to give an amide of Formula 7.
In a further aspect, isocyanates or isothiocyanates (Method E), or alkylhalides (Method F) are used in the presence of a base to form products of Formula 7.
Hydrolysis of the ester group R in Formula 7 can be carried out using routine procedures, as outlined in Scheme 2, Step b), for example by stirring with aqueous sodium hydroxide, or trifluoroacetic acid to give a compound of general Formula (I).
Alternatively, tetrahydropyridoindoles of general Formula (I) can be synthesized in three consecutive steps as outlined in Scheme 3, starting from abovementioned Fischer indole product of Formula 3, which is reacted first in a substitution reaction with abovementioned reagent of Formula L-R5, using conditions as described in Methods A to F, to give a compound of Formula 8. Subsequent alkylation of the indole nitrogen can be performed with a compound of the abovementioned Formula L-CH2CO2R, in which R and L is as defined above, under conditions as described in Scheme 1 for the alkylation of compound of Formula 4, to give a precursor of Formula 7. Final deprotection under standard conditions, as outlined in Scheme 2, Step b) delivers a compound of general Formula (I).

upon standing and is used in the next step without further purification. tR (LC-2) 2.31 min; ESI-MS (positive ion): m/z 295.37 [M+Na]+ (calcd 272.34 for Ci6H2oN202).
lc) Ethyl (2-tert-butoxycarbonyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetyl
To a stirred suspension of crude 2-tert.-butoxycarbonyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol (33.5 mmol) and caesium carbonate (25.1 g, 77.1 mmol) in dry acetone is added ethyl bromoacetate (5.6 ml, 50,3 mmol). The reaction mixture is stirred at rt overnight and then filtered over a small plug of Celite. The filtrate is concentrated under reduced pressure and the residue is purified by silica gel column chromatography (hexane/ EtOAc 5:1) to afford pure sub-title compound as yellow oil (8.45 g) in 70% yield (over two steps). tR (LC-2) 2.46 min; ESI-MS (positive ion): m/z 381.54 [M+Naf (calcd 358.43 for C20H26N2O4).
Intermediate 2: Ethyl (8-bromo-l,2,3,4-tetrahydro-pyrido[4,3-i]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 4-bromophenylhydrazine for phenylhydrazine in Step la).
Intermediate 3: Ethyl (8-methyl-l,2,3,4 -tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 4-methylphenylhydrazine for phenylhydrazine in Step la).
Intermediate 4: Ethyl (7-methyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 3-methylphenylhydrazine for phenylhydrazine in Step la).
Intermediate 5: Ethyl (7-chloro-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride

The title compound is prepared using a procedure analogous to Intermediate 1, substituting 3-chlorophenylhydrazine for phenylhydrazine in Step la).
Intermediate 6: Ethyl (8-chloro-l,2,3,4-tetrahydro-pyrido[4,3-6]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 4-chlorophenylhydrazine for phenylhydrazine in Step la).
Intermediate 7; Ethyl (6-chloro-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 2-chlorophenylhydrazine for phenylhydrazine in Step la).
Intermediate 8: Ethyl (8-fluoro-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 4-fluorophenylhydrazine for phenylhydrazine in Step la).
Intermediate 9: Ethyl (6-methyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 2-methylphenylhydrazine for phenylhydrazine in Step la).
Intermediate 10: Ethyl (7-fluoro-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 3-fluorophenylhydrazine for phenylhydrazine in Step la).

Intermediate 11: Ethyl (7,8-dichloro-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 3,4-dichlorophenylhydrazine for phenylhydrazine in Step la).
Intermediate 12: Ethyl (8-trifiuoromethyl-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 4-trifluoromethylhydrazine for phenylhydrazine in Step la).
Intermediate 13: Ethyl (8-tert-butyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yI)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 4-tert-butylhydrazine for phenylhydrazine in Step la).
Intermediate 14: Ethyl (7-Chloro-8-methyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 3-chloro-4-methylhydrazine for phenylhydrazine in Step la).
Intermediate 15: Ethyl (7,8-dimethyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride
The title compound is prepared using a procedure analogous to Intermediate 1, substituting 3,4-dimethylhydrazine for phenylhydrazine in Step la).
Intermediate 16: Ethyl (8-isopropyl-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetate hydrochloride

The title compound is obtained using conditions for the hydrolysis of the above crude analogous to Example 1: tR (LC-1) 2.22 min; ESI-MS (positive ion): m/z 387.14 [M+Na]+ (calcd 364.40 for C21H20N2O4).
Examples 3-5 of the following Table 1 are prepared using a procedure analogous to that described for Example 2, substituting the appropriate chloroformates for benzyl chloroformate.

Step b): A solution of crude ethyl (2-benzoyl-1,2,3,4-tetrahydro-pyrido[4,3-6]indol-5-yl)-acetate (0.085 mmol) in THF (0.5 ml) is treated with 0.2 N aqueous NaOH solution (0.64 ml) at rt for 15 min. Then, the yellow reaction mixture is diluted with water (2 ml), washed with diethyl ether (2 mi), acidified with cone. HC1 to pH 1 and extracted with dichloromethane. The combined organic phases are washed with water, then dried over Na2SO4, filtered and the solvent evaporated. The crude product is recrystallized from diisopropyl ether to give pure title compound as yellow solid: tR (LC-1) 2.95 min; ESI-MS (positive ion): m/z 335.17 [M+H]+ (calcd 334.37 for C20H18N2O3).
Examples 7-31 of the following Table 2 are prepared using a procedure analogous to that described for Example 6, substituting the appropriate acid chloride for naphthoylchloride.

Step b): The title compound is obtained using conditions for the hydrolysis of the above ester analogous to Example 1: tR (LC-2) 2.47 min; ESI-MS (positive ion): m/z 431.22 [M+H]+ (calcd 430.55 for C27H30N2O3).
Examples 38-52 of the following Table 4 are prepared using a procedure analogous to that described for Example 37, substituting the appropriate acid for cyclohexylphenylacetic acid.

Table 6
Examples 68-96 of the following Table 7 are prepared using a procedure analogous to that described for Example 6, substituting the appropriate acid chloride for naphthoylchloride and substituting the appropriate Intermediate for Intermediate 1.

Table 7
Examples 97-106 of the following Table 8 are prepared using a procedure analogous to that described for Example 32, substituting the appropriate Intermediate for Intermediate 1 and the appropriate phenyihydrazine for 4-methoxyphenylhydrazine,

Table 8
Examples 107-149 of the following Table 9 are prepared using a procedure analogous to that described for Example 53, substituting the appropriate acid for 2-ethoxynaphthoic acid.

Table 9
Examples 150-171 of the following Table 10 are prepared using a procedure analogous to that described for Example 57, substituting the appropriate isocyanate or isothiocyanate, respectively, for phenyl isocyanate.

Table 10 Table 11: NMR data of Intermediates 1-8 are given below.

Biological assay;
Preparation of CRTH2 membranes and radioligand binding assay:
Preparation of the membranes and radioligand binding assays are performed according to known procedures, e.g. Sawyer N. et al. (Br. 1 Pharmacol, 2002,137,1163-1172). A clonal HEK 293 cell line, expressing high level of recombinant hCRTH2 receptor, is selected for the preparation of membranes. Cells are detached from culture plates in 5 ml buffer A per plate (5 mM Tris, 1 mM MgCl2x6 H2O, 0.1 mM PMSF, 0.1 mM phenanthroline) using a police rubber and transferred into centrifugation tubes and frozen at -80°C. After thawing, the cells are centrifuged at 500 g for 5 min and then resuspended in buffer A. Cells are then fragmented by homogenization with a Polytron homogenizer for 30 s. The membrane fragments are centrifuged at 3000 g for 40 min and resuspended in membranes in buffer B (50 mM Tris, 25 mM MgCb, 250 mM saccharose, pH 7.4) and aliquots are stored frozen.
Binding assay is performed in a total volume of 250µl. In each well, 75 µl buffer C (50 mM Tris, 100 mM NaCl, 1 mM EDTA, 0.1% BSA (protease free), 0.01 % NaN3, pH 7.4) is mixed with 50 µl {3H}-PGD2 (at 2.5 nM (220.000 dpm per well) from Amersham, TRK734), 100 µl CRTH2 membranes to give 80 µg per well and 25 µl of test compound in buffer C containing 1% DMSO. For unspecific binding, PGD2 is added to the reaction mixture at 1 µM final concentration. This binding assay mix is incubated at rt for 90 min and then filtered through a GF/C filter plate. The filter is washed three times with ice cold binding buffer. Then, 40 µl per well Microscint-40 (Packard) are added and the bound radioactivity is quantified by means of Topcount (Packard).

Test for antagonist binding to the CRTH2 receptor:
Compounds of Formula (I) display IC50 values in the range of 0.1 nM to 1 µM, especially in the range of 1 nM to 100 nM. The following Table 13 exemplifies IC50 values of compounds of the present invention.

Table 13
Intracellular calcium mobilization assay (FLIPR):
Cells (HEK-293), stably expressing the hCRTHfe receptor under the control of the cytomegalovirus promotor from a single insertion of the expression vector pcDNA5 (Invitrogen), are grown to confluency in DMEM (low glucose, Gibco) medium supplemented with 10% fetal calf serum (both Bioconcept, Switzerland) under standard mammalian cell culture conditions (37°C in a humidified atmosphere of 5% CO2). Cells are detached from culture dishes using a dissociation buffer (0.02% EDTA in PBS, Gibco) for 1 min, and collected by centrifugation at 200 g at it for 5 min in assay buffer [equal parts of Hankfs BSS (HBSS, Bioconcept) and DMEM (low glucose, without phenol red, Gibco)]. After incubation for 45 min (37°C and 5% CO2) in the presence of 1 |xM Fluo-4 and 0.04% Pluronic F-127 (both Molecular Probes), 20mM HEPES (Gibco) in assay buffer, the cells are washed with and resuspended in assay buffer, then seeded onto 384-well FLIPR assay plates (Greiner) at 50,000 cells in 66 pi per well, and sedimented by centrifugation.
Stock solutions of test compounds are made up at a concentration of 10 mM in DMSO, and serially diluted in assay buffer to concentrations required for inhibition dose response curves. Prostaglandin D2 (Biomol, Plymouth Meeting, PA) is used as an agonist.
A FLIPR384 instrument (Molecular Devices) is operated according to the manufacturer's standard instructions, adding 4 pi of test compound dissolved at 10mM in DMSO and diluted prior to the experiment in assay buffer to obtain the desired final concentration. 10µl of 80 nM prostaglandin D2 (Biomol, Plymouth Meeting, PA) in assay buffer, supplemented with 0.8% bovine serum albumin (fatty acid content
obtain a final concentration of lOnM and 0.1 %, respectively. Changes in fluorescence are monitored before and after the addition of test compounds at λex=488 nm and λem=540 nm, Emission peak values above base level after prostaglandin D2 addition are exported after base line subtraction. Values are normalized to high-level control (no test compound added) after subtraction of base line value (no prostaglandin D2 added). The program XLlfit 3.0 (IDBS) is used to fit the data to a single site dose response curve of the equation (A+((B-A)/(l+((C/x)AD)))) and to calculate the IC50 values.
Antagonist analysis
Compounds of general Formula (I) antagonize prostaglandin D2 mediated hCRTH2 receptor activity with an IC50 of less than 10 µM, especially less than 300 nM as exemplified in the following Table 14.

Claims:
1. A compound selected from the group consisting of tetrahydropyridoindole derivatives of the general Formula (I)

R5 represents C0-C5-alkyl-carbonyl; C1-C5alkyl-carbamoyl; C1-C5alkoxy-carbonyl; C2-C5-alkenyl-carbonyl; C3-Cb-cycloalkyl-carbonyl; C3-C6-cycloalkyl-C1-C3-alkyl-carbonyl; C3-Cb-cycloalkyl-carbamoyl; C3-Cb-cycloalkyl-thiocarbamoyl; phenyl-C1-C3-alkyl; phenyl-carbonyl or phenyl-C1-C3-alkyI-carbonyl wherein the phenyl moiety of these two groups may be mono-, di-, tri- or tetra-substituted by substituents independently selected fromC1-C4alkyl, C1-C3-alkoxy, halogen, trifluoromethyl and trifluoromethoxy, mono-substituted by C3-Cb-cycloalkyl, or mono-substituted by a phenyl group which in turn may be substituted by a C1-C3-alkyl or C1-C3-alkoxy group; phenyl-C1-C3-alkoxy-carbonyl; phenyl-carbamoyl or phenyl-thiocarbamoyl wherein these two groups are optionally independently mono- or poly-substituted by C1-C5-alkyl and/or halogen; phenyl-CrC3-alkyl-carbamoyl; phenyl-C1-C3-alkyl-thiocarbamoyl; biphenyl-carbamoyl; naphthyl-carbonyl, naphthyl-C1-C3-alkyl-carbonyl or naphthyl-carbamoyl wherein the naphthyl moieties of these three groups are optionally mono- or poly-substituted by substituents independently selected from C1-C3-alkyl, C1-C3-alkoxy and halogen; fluorenyl-carbonyl, optionally substituted by oxo; fluorenyl-C1-C3-alkoxy-carbonyl; or five- to nine-membered heteroaryl-carbonyl groups containing one to three heteroatoms independently selected from oxygen, nitrogen and sulfur wherein said groups may be substituted by one or two groups independently selected from C1-C3-alkyl, C1-C3-alkoxy, halogen and trifluoromethyl; with the proviso that when R1 , R2 , R3 and R4 represent hydrogen, R5 is not an ethoxy-carbonyl group or a tert.-butoxycarbonyl group.
9. A compound according to claim 1 or 2, wherein
R1 , R2 , R3 and R4 independently represent hydrogen, C1-C5-alkyl, C1-C3-alkoxy or halogen; and R5 represents C0-C5-alkyl-carbonyl; C1-C5-alkoxy-carbonyl; C2-Cs-alkenyl-carbonyl; C3-Cb-cycloalkyl-carbonyl; C3-C6-cycloalkyl-C1-C3-alkyl-carbonyl; C3-C6-cycloaIkyl-C1-C3-alkoxy-carbonyl; phenyl-carbonyl or phenyl-C1-C3-alkyl-carbonyl wherein the phenyl moiety of said groups may be independently mono-, di- or tri-substituted by C1-C4-alkyl, C1-C3-alkoxy, halogen, trifluoromethyl or trifluoromethoxy, or mono-substituted by a phenyl group which in turn may be substituted by a C1-C3-alkyl or C1-C3-alkoxy group; naphthyl-carbonyl; fluorenyl-C1-C3-alkoxy-carbonyl; or five- or six-membered heteroaryl-carbonyl groups containing one to three heteroatoms independently selected from oxygen, nitrogen and sulfur wherein said groups may be substituted by one or two groups independently selected from C1-C3-alkyl, C1-C3-alkoxy, halogen and trifluoromethyl;
with the proviso that when R1 , R2, R3 and R4 represent hydrogen, R5 is not an ethoxy-carbonyl group or a tert.-butoxycarbonyl group.
10. A compound according to any one of the preceding claims selected from the group consisting of:(2-benzyloxycarbonyl-l, 2,3,4-tetrahydro-pyrido[4?3-b]indol-5-yl)-acetic acid; (2-butoxycarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid; (2-9H-fluoren-9-ylmethoxycarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;(2-acetyl-l ,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid; (2-phenylacetyl-l, 2, 3, 4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid; (2-benzoyl-1, 2, 3, 4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid; [2-(3,4,5-trimethoxy-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid; (2-cyclohexanecarbonyl-l, 2, 3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid; [2-(4-methoxy-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid; [2-(thiophene-2-carbonyl)4,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid; [2-(furan-2-carbonyl)-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic acid; (2-cyclopropanecarbonyl-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid; [2-(naphthalene-l-carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid; [2-(2-methoxy-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid; [2-(4-trifluoromethyl-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic acid;[2-(3,5-bis-trifluoromethyl-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic acid;
[2
(2-hexanoyl-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-acetic acid;
[2-(3-chloro-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(4-bromo-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(pyridine-3-carbonyl)-l,2,3,44etrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
(2-benzoyl-8-methoxy-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-aceticacid;
(2-benzoyl-7-methyl-1,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-aceticacid;
(2-benzoyl-8-bromo-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-aceticacid;
(2-benzoyl-8-methyl-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-aceticacid;
(2-benzoyl-6-methyI-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl)-aceticacid;
[2-(pyrazine-2-carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-aceticacid;
[2-(2-bromo-3-methyl-benzoyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic
acid;
[2-(4'-ethyl-biphenyl-4-carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic
acid;
[2-(2-bromo-5-methyl-benzoyI)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic
acid;
[2-(2-chloro-b-methyl-pyridine-4-carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-
yl]-acetic acid;
[2-(biphenyl-2-Carbonyl)-l,2,3,4-tetrahydro-pyrido[4,3-b]indol-5-yl]-acetic acid